Engine shutdown valves are well known in the diesel engine industry. Such valves are used to terminate the operation of a diesel engine when overrevving results from combustible vapours being present in the atmosphere in which such engines are operated or when other mechanical failures may occur or be imminent. By terminating atmospheric or air flow through the intake manifold in which combustible vapours are present, the engine will starve from lack of oxygen and the engine will shutdown thereby preventing damage to the engine caused by overrevving. Such engine shutdown valves are, for example, disclosed in our U.S. Pat. Nos. 4,215,845, 4,285,494, 4,537,386 and 5,203,536.
In U.S. Pat. No. 5,203,536, there is disclosed an engine shutdown valve which utilises a tension spring to close the gate to which it is attached and to thereby terminate air flow through the intake manifold of the engine. However, when the gate is in its usual open position, the tension spring was fully extended and, in this extended position, it was vulnerable to engine vibration. This was disadvantageous. A further disadvantage in the valve disclosed in the aforementioned '536 patent is that the tension spring was not accessible from the outside of the housing of the shutdown valve. The shutdown valve was required to be completely disassembled to obtain access to the tension spring for replacement or adjustment.